add compile-time interface satisfaction assertions for public types

Add var _ Interface = (*ConcreteType)(nil) assertions for:
- *flamegraph.LiveTrie → runtime.{Snapshotter,Configurator,LiveTrieSource}
  and tui/flamegraph.{Snapshotter,Configurator,LiveTrieSource}
- *probemanager.Manager → runtime.ProbeManager
- *statsengine.Engine → runtime.SnapshotSource
- *streamrow.RingBuffer → runtime.EventSink
- *runtimeBindings (tui) → runtime.TraceRuntimeBindings
- *lateBoundDashboardSource → dashboard.SnapshotSource
- libbpfTracepointProgram/Module → probemanager.{Program,Attacher}

Assertions are grouped close to their interface definitions to avoid
introducing new import cycles (runtime already imports all affected
packages; tui/flamegraph already imports coreflamegraph).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

4 files changed, 71 insertions, 0 deletions

diff --git a/internal/ior_bpfsetup.go b/internal/ior_bpfsetup.go
index d5f3be8..885d321 100644
--- a/internal/ior_bpfsetup.go
+++ b/internal/ior_bpfsetup.go
@@ -97,3 +97,16 @@ func setupEventChannel(bpfModule *bpf.Module) (chan []byte, error) {
 	rb.Poll(300)
 	return ch, nil
 }
+
+// --- compile-time interface satisfaction assertions ---
+//
+// These blank-identifier assignments cause a build error if the libbpf wrapper
+// types drift out of sync with the probemanager interfaces they satisfy.
+
+var (
+	// libbpfTracepointProgram wraps a *bpf.BPFProg as a probemanager.Program.
+	_ probemanager.Program = (*libbpfTracepointProgram)(nil)
+
+	// libbpfTracepointModule wraps a *bpf.Module as a probemanager.Attacher.
+	_ probemanager.Attacher = (*libbpfTracepointModule)(nil)
+)
diff --git a/internal/runtime/runtime.go b/internal/runtime/runtime.go
index 5e6f2a4..307c012 100644
--- a/internal/runtime/runtime.go
+++ b/internal/runtime/runtime.go
@@ -186,3 +186,31 @@ func TraceFiltersFromContext(ctx context.Context) (globalfilter.Filter, bool) {
 	}
 	return filters.filter.Clone(), true
 }
+
+// --- compile-time interface satisfaction assertions ---
+//
+// These blank-identifier assignments cause a build error if any concrete type
+// drifts out of sync with the interface it claims to satisfy. They are grouped
+// here because the runtime package already imports every relevant package
+// (*flamegraph.LiveTrie, *probemanager.Manager, *statsengine.Engine, and
+// *streamrow.RingBuffer), keeping the assertions co-located with the interface
+// definitions without introducing new import cycles.
+
+var (
+	// *flamegraph.LiveTrie must satisfy both the read-only and mutating sides of
+	// the trie contract as well as the combined LiveTrieSource interface.
+	_ Snapshotter   = (*flamegraph.LiveTrie)(nil)
+	_ Configurator  = (*flamegraph.LiveTrie)(nil)
+	_ LiveTrieSource = (*flamegraph.LiveTrie)(nil)
+
+	// *probemanager.Manager must satisfy the probe-control surface exposed to the TUI.
+	_ ProbeManager = (*probemanager.Manager)(nil)
+
+	// *statsengine.Engine must satisfy the snapshot-source contract used by the
+	// dashboard and the TUI runtime.
+	_ SnapshotSource = (*statsengine.Engine)(nil)
+
+	// *streamrow.RingBuffer must satisfy the full event-sink contract (read +
+	// write sides), which is a superset of StreamSource.
+	_ EventSink = (*streamrow.RingBuffer)(nil)
+)
diff --git a/internal/tui/flamegraph/model.go b/internal/tui/flamegraph/model.go
index 68ce7fd..73285f9 100644
--- a/internal/tui/flamegraph/model.go
+++ b/internal/tui/flamegraph/model.go
@@ -113,6 +113,19 @@ type LiveTrieSource interface {
 	Configurator
 }
 
+// --- compile-time interface satisfaction assertions ---
+//
+// *coreflamegraph.LiveTrie is the sole production implementation of all three
+// trie interfaces. The assertions are placed here rather than in the
+// flamegraph package itself to avoid an import cycle: runtime imports
+// flamegraph, so flamegraph cannot import runtime. The tui/flamegraph package
+// already imports coreflamegraph, making it the natural home.
+var (
+	_ Snapshotter    = (*coreflamegraph.LiveTrie)(nil)
+	_ Configurator   = (*coreflamegraph.LiveTrie)(nil)
+	_ LiveTrieSource = (*coreflamegraph.LiveTrie)(nil)
+)
+
 type zoomState struct {
 	path                string
 	previousSelectedIdx int
diff --git a/internal/tui/tui.go b/internal/tui/tui.go
index 6124fcd..eee4252 100644
--- a/internal/tui/tui.go
+++ b/internal/tui/tui.go
@@ -1247,6 +1247,23 @@ func placeToViewport(width, height int, content string) string {
 	return lipgloss.Place(width, height, lipgloss.Left, lipgloss.Top, content)
 }
 
+// --- compile-time interface satisfaction assertions ---
+//
+// These blank-identifier assignments cause a build error if any concrete type
+// drifts out of sync with the interface it claims to satisfy.
+
+var (
+	// *runtimeBindings must satisfy the full TUI runtime contract, which
+	// composes RuntimePublisher (write side) and RuntimeState (read side).
+	_ runtime.TraceRuntimeBindings = (*runtimeBindings)(nil)
+
+	// lateBoundDashboardSource must satisfy the SnapshotSource contract used
+	// by the dashboard model. It wraps the injected stats engine and forwards
+	// calls through runtimeBindings so the dashboard source can be wired
+	// before the actual engine is available.
+	_ dashboardui.SnapshotSource = (*lateBoundDashboardSource)(nil)
+)
+
 func altScreenView(content, title string) tea.View {
 	view := tea.NewView(content)
 	view.AltScreen = true